The old man tells Alicia that her Browning Hi-Power pistol would not fire because the safety catch was engaged. Later, he says that all Alicia had needed to do is load a round into the firing-chamber. On the Browning Hi-Power pistol, releasing the safety catch does not load a round into the firing-chamber.
When Alicia uses the Fire Extinguisher on Irving Wallace, he falls and grabs a power cable to climb back up. In the wide shot of Irving Wallace climbing back up, in the far right corner of the frame, you can clearly see a cable, hoisting him up as he climbs up the cable.
It's obviously a dummy when the girl get torn in two pieces in the attic. When her torso lies on the floor and the guy next to her stands up, he kicks it by mistake. It then moves very easy and doesn't seem to be heavy as a human body (or half a human body).